A feed is necessary in order to perform the distillation. The phase state of the feed must not necessarily be liquid. It can be vapour as well.
Depending on the feed temperature or pressure, a liquid-feed can either be a sub-cooled liquid or saturated liquid. A saturated liquid simply means that it is available at its boiling point and about to vaporise.
In addition to that, a feed can also be a vapour. Again, depending on temperature or pressure, that feed can also contain two phases in a certain ratio, it can be a saturated vapour and a superheated vapour. These different types of feed are important if we want to use McCabe-Thiele diagram in order to determine parameters such reflux ratio and number of stages, just to name a few.
With the help of total mass balance and the mass balance for each component, a feed line can be obtained. It is a again a straight line. To be able to extract necessary information from the McCabe-Thiele diagram, both operating line and feed line are crucial.
Depending on the feed phase, the feed line can either have a positive slope or a negative slope(zero and infinite also possible). In order to see the influence of the feed on the feed line in the McCabe-Thiele diagram, a diagram would be helpful:
There are 5 different feed lines, a,b,c,d,e in the diagram above.
a) sub-cooled liquid feed
b) saturated liquid feed
c) two phases feed
d) saturated vapour feed.
e) superheated vapour feed
Depending on the feed temperature or pressure, a liquid-feed can either be a sub-cooled liquid or saturated liquid. A saturated liquid simply means that it is available at its boiling point and about to vaporise.
In addition to that, a feed can also be a vapour. Again, depending on temperature or pressure, that feed can also contain two phases in a certain ratio, it can be a saturated vapour and a superheated vapour. These different types of feed are important if we want to use McCabe-Thiele diagram in order to determine parameters such reflux ratio and number of stages, just to name a few.
With the help of total mass balance and the mass balance for each component, a feed line can be obtained. It is a again a straight line. To be able to extract necessary information from the McCabe-Thiele diagram, both operating line and feed line are crucial.
Depending on the feed phase, the feed line can either have a positive slope or a negative slope(zero and infinite also possible). In order to see the influence of the feed on the feed line in the McCabe-Thiele diagram, a diagram would be helpful:
There are 5 different feed lines, a,b,c,d,e in the diagram above.
a) sub-cooled liquid feed
b) saturated liquid feed
c) two phases feed
d) saturated vapour feed.
e) superheated vapour feed
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